On October 23, the FDA approved a new biologic follow-on agent that may significantly affect the US biosimilar industry. Monday’s approval of Celltrion’s subcutaneous (SC) form of infliximab could upset the apple cart on biosimilars uptake in this important drug category.
The new drug, dubbed Zymfentra® (the nonproprietary name, infliximab-dyyb, is the same as for IV Inflectra®), was the subject of two randomized, double-blind, controlled, phase 3 studies in ulcerative colitis and Crohn’s disease. Each of these investigations tested the product and its effects against placebo—not the reference product or biosimilar—demonstrating significant improvement in patient’s disease symptoms and endoscopic evaluations.
One possible drawback of this product is that in order for SC Zymfentra to be used, the indication calls for initial induction dosing of infliximab with the infusible form. Therefore, SC infliximab may not be considered a complete replacement for the infusible formulations available today.
As reported earlier, Celltrion USA intends to market the product through its internal sales force, not with a commercialization partner. Celltrion has not yet announced a launch date or pricing. However, it is expected to compete directly with its own Inflectra, which is marketed by Pfizer in the US, as well as Renflexis®, Avasola®, and the reference agent Remicade® (and Janssen’s unbranded version).
Celltrion USA applied for approval of Zymfentra via the 351(a) pathway, as opposed to the 351(k) biosimilar approval pathway. Technically, no reference product exists for an SC infliximab formation, as SC Remicade was never approved. Thus Zymfentra is more accurately called a follow-on.
This SC formulation of infliximab was approved in Europe for the treatment of inflammatory bowel disease in 2021; however, uptake has not been as rapid as hoped in the EU. In the US, Zymfentra will be covered and managed under the pharmacy benefit, which health plans generally prefer, as it avoids the provider buy-and-bill scenario and allows payers to utilize specialty pharmacy services. This may help jumpstart Zymfentra’s market uptake. Presently, roughly half of infliximab prescribing in the US is for a biosimilar.